More specifically, his nomination has left supporters of pot legalization troubled about what his confirmation could mean for the future of legalization efforts at the state level given that the drug remains illegal under federal law.

"(I)t couldn't be much worse for the marijuana law reform movement and our recent legalization victories," said Erik Altieri, Executive Director of NORML -- an advocacy group that supports legalization of the drug -- in a post on the group's website.

'Good people don't smoke marijuana'

Sessions has not kept his strong feelings against marijuana use a secret.

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"Good people don't smoke marijuana," Sessions said during a Senate hearing in April. "We need grown ups in Washington to say marijuana is not the kind of thing that ought to be legalized, it ought not to be minimized, that it is in fact a very real danger."

In 2014, Sessions also took aim at FBI Director James Comey for making a joke at a hearing about the FBI having to relax its marijuana rules if it wanted to attract more young people to join the bureau.

"Do you understand that that could be interpreted as one more example of leadership in America dismissing the seriousness of marijuana use?" Sessions asked. "And that could undermine our ability to convince young people not to go down a dangerous path?"

Separately, a Justice Department staffer once claimed Sessions said in the 1980s he thought the Ku Klux Klan "were OK until I found out they smoked pot."

Sessions' office did not immediately respond to a request for comment for this story.

Federal law is 'crystal clear'

While roughly half of US states and the District of Columbia have decriminalized or legalized marijuana use, it remains illegal under federal law and, if confirmed, the Alabama senator will hold the power over the federal enforcement arm of criminal laws, such as the Controlled Substances Act.

The marijuana industry currently benefits from a legal memorandum issued by the Justice Department in 2013 that essentially adopted a policy of non-interference with marijuana-friendly state laws, so long as they don't threaten other federal priorities, such as preventing the distribution of the drug to minors and supporting cartels. But a Justice Department with Sessions at the helm has the ability to rip this up and simply issue a new memo -- reverting back to the old regime where states were left in a more precarious position.

John Hudak, deputy director of the Center for Effective Public Management and a senior fellow at the Brookings Institution who studies marijuana policy, points out that Sessions could not only empower federal prosecutors across the country to begin targeting drug crimes again, but if the Justice Department sues individual states, it is unlikely to lose that battle in court.

"The law is crystal clear on this -- what states are doing is a federal crime," Hudak told CNN in an interview Friday.

Brian Vicente, a Denver-based marijuana industry attorney, explained that the cloud of prosecution hangs over the heads of many proponents of the drug, especially those who use medical marijuana.

"Medical marijuana patients are scared," Vicente told CNN. "They're scared they are going to be arrested by (federal agents) for following their doctor's orders."

Will Trump save pot?

The question on many industry groups' minds Friday is whether Trump will serve as a check on Sessions' staunch opposition to marijuana use.

"President-elect Trump has said on multiple occasions that he respects states' right to establish their own marijuana policies. We would expect appointees who serve at the pleasure of the president to stick to the president's position on this subject," said Mason Tvert of the Marijuana Policy Project in a statement to CNN.

Others suggest he will see the majority of Americans support legalization efforts.

"If Trump is smart about this, he is going to look at the political landscape and say a lot of people support this," Hudak told CNN Friday.

Meanwhile, others expressed hope that attacking marijuana use would simply take a back seat in Trump's administration given all of the other issues on his plate.

"I hope this administration maintains the status quo," said Hilary Bricken, an attorney in Seattle who represents marijuana businesses. "But with a Republican majority-controlled Congress, if (Sessions) wants to say the war on drugs is back on, he won't face much opposition."